Význam tématu
Gasová chromatografie vybavená methanátorem umožňuje citlivou detekci CO a CO₂ pomocí FID. In-jet methanátor Jetanizer™ nabízí ekologičtější a odolnější alternativu k tradičním Ni katalyzátorům a rozšiřuje linearitu stanovení od nízkých ppm po procentní koncentrace.
Cíle a přehled studie
Cílem analýzy bylo ověřit limity detekce, kvantifikace a linearitu Jetanizer™ na GC-2030 pro permanentní plyny (O₂, N₂), CO, CO₂, CH₄ a C₂ uhlovodíky (ethan, ethylen, acetylen) na různých kapilárních i plněných kolonách.
Použitá instrumentace
- Shimadzu GC-2030 s ventilem LVO-2030
- In-jet methanátor Jetanizer™ jako přímá náhrada FID jetu
- FID s toky: He (make-up 24 mL/min), H₂ (32 mL/min), Air (250 mL/min)
- Kapilární kolony: HP-Plot MS-5A, CP-Molsieve 5A, GS-CarbonPLOT, CarboBond
- Plněná kolona: Carboxen 1006 (1 m × 1/8″)
Použitá metodika
Pro každou kolonovou fázi byly nastaveny izotermní podmínky (60–100 °C), lineární rychlost helia ~36,6 cm/s, split ratio 7:1 (kapilární) nebo 0,7:1 (plněná), injekční objem 1 mL. Kalibrace proběhla v rozsahu ~0,87 ppm až 99,99 % dle plynu, za účelem stanovení linearity, LOD a LOQ.
Hlavní výsledky a diskuse
- Kapilární MS-5A vykazovala non-linearitu CO mezi 6 % a 20 %, ostatní plyny byly lineární.
- CP-Molsieve 5A prokázala odlišnou linearitu CO a CH₄ ve středních koncentracích, naznačující závislost na fázi kolony.
- Kolony GS-CarbonPLOT a CarboBond poskytly vysokou linearitu napříč celým rozsahem, pouze extrémy CO₂ způsobily přetížení.
- LOD/LOQ pro CH₄ a CO dosahovaly sub-ppm hodnot na kapilárách i plněné koloně, plněná kolona vykázala mírně lepší citlivost.
- Jetanizer™ nevykazoval projevy otravy kyslíkem ani sírou během testu, prokazujíc svou vyšší odolnost oproti tradičním methanátorům.
Přínosy a praktické využití metody
Jetanizer™ umožňuje rychlou a nenáročnou integraci do GC-2030 bez dalšího hardware. Široký lineární rozsah a nízké detekční limity jsou výhodné pro průmyslové, environmentální a QA/QC aplikace.
Budoucí trendy a možnosti využití
- Optimalizace split ratio pro eliminaci přetížení kolony při vysokých koncentracích
- Rozšíření spektra analyzovatelných plynů a nižší detekční limity
- Přenosné GC systémy s in-jet methanátorem pro on-site měření
- Automatizované online monitorování emisí a kvality vzduchu
Závěr
Jetanizer™ se ukázal jako efektivní a odolná alternativa k tradičním Ni methanátorům v GC-FID. Nabízí rozšířenou linearitu, vysokou citlivost a nižší provozní nároky bez nutnosti složitých úprav.
Obsah byl automaticky vytvořen z originálního PDF dokumentu pomocí AI a může obsahovat nepřesnosti.
No. SSI-GC-2103
■ Background
Utilizing a methanizer in a gas chromatograph,
carbon monoxide and carbon dioxide can be
converted to methane which allows them to be
detected by a flame ionization detector (FID) providing
higher sensitivity over detection with a thermal
conductivity detector (TCD). Traditional methanizers
use an activated nickel catalyst that is toxic to the
environment and is susceptible to poisoning from
analytes such as oxygen and sulfurs, which reduces its
effectiveness. Additionally, the response generated
from traditional methanizers with FID have a limited
range of linearity.
Activated Research Company® (ARC) produces an in-
jet methanizer, the Jetanizer™, which uses a
proprietary catalyst material that purports to be a
more environmentally friendly and more robust
methanizer that offers linearity over low ppm to high
percentage concentrations of carbon monoxide and
carbon dioxide. This analysis will assess the limits of
detection and quantification of carbon monoxide,
carbon dioxide, methane and C2 hydrocarbons
(ethane, ethylene, and acetylene) using the
Jetanizer™ on the GC-2030.
■ Instrumentation
The GC-2030 gas chromatograph equipped with an
LVO-2030, and 6-port gas loop sampling valve was
used for this analysis. The Jetanizer™ is a drop-in
replacement for the traditional GC-2030 FID jet which
requires no additional hardware or special plumbing.
Both capillary and packed columns were used in this
analysis to test the capabilities of the Jetanizer™.
To determine the effects of the capillary column phase
on the analysis, two different PLOT column phases
were used for this analysis, molecular sieve and
carbonized molecular sieve. Two different columns of
each PLOT phase were used to address if a specific
column had any effect on the Jetanizer™ linearity. To
confirm the viability of packed column analysis, a
custom 1 m carbonized molecular sieve column was
used.
For both capillary and packed columns, a ~20 cm
piece of 0.53 mm ID MXT tubing was joined with a
union to the end of the analytical column and installed
in the FID. This capillary tubing acted as a guard
column protecting the end of the column from the
high operating temperatures of the Jetanizer™ and to
serve as a particle trap for any residual particles
evolved from the columns used in the analysis. The
guard column insertion depth into the FID was 45 mm
to ensure the eluting analytes would encounter the
catalyst bed in the Jetanizer™
■ Experimentation and Observation
Gas standards containing carbon monoxide,
methane, and carbon dioxide at various
concentrations were utilized for this analysis. The
concentrations tested ranged from 1 ppm up to
99.99%.
Capillary Column Analysis
A total of four capillary columns were used to test the
effects of specific columns on the overall response of
the Jetanizer™. Two molecular sieve columns were
used, and two carbonized molecular sieve columns
were used. Linearity and limits of detection and
quantitation were determined for each column.
System GC
Analysis and Characterization of ARC’s In-
jet Methanizer for Permanent Gases,
Carbon Dioxide, and Light Hydrocarbons
No. GC-2103
No. SSI-GC-2103
Molecular sieve column
A calibration curve to test the linearity of the
Jetanizer™ with molecular sieve columns was
produced from a 0.96 ppm to approximately 20% for
carbon monoxide and 0.87 ppm to approximately
15% for methane.
A linear regression analysis was performed for each
calibration curve. The following method conditions
were used:
Table 1: Method Parameters for Molecular sieve PLOT Column
Parameter
Value
Column
HP-Plot MS-5A 30 m X 0.53 mm X 50 μm (19095P-MS0),
CP-Molsieve 5A 25 m X 0.53 mm X 50 μm (CP7538)
Valve Box Temperature
80° C
Injection Volume
1 mL gas sampling loop
Injector Temperature
200° C
Linear Velocity
36.6 cm/sec He
Split Ratio
7:1
Oven Ramp
Isothermal 100° C
FID Temperature
400° C
FID Gas Flows
Makeup (He): 24 mL/min, H2: 32 mL/min, Air: 250 mL/min
FID Column Insertion Depth
45 mm
Table 2: Concentrations used for calibration curve for Molecular Sieve Columns
Concentration of Standards (ppm)
Analytes
Low TOGAS
Standard 1
Low ppm Std
Standard 2
12% CO2
Standard 3
14% CO2
Standard 4
8% CO2
Standard 5
High TOGAS
Standard 6
Carbon
Monoxide
100 0.96
59800
9900
199900
4200
Methane
100 0.87
149900
60100
11900
4200
Carbon Dioxide
400 2.55
120100
140100
78900
20000
Figure 1A: Representative Stacked Calibration Curve
Chromatograms for HP-PLOT MS5A
Figure 1B: Calibration curve for methane using the HP-PLOT
MS5A
Figure 1C: Calibration curve for carbon monoxide using the
HP-PLOT MS5A
It was noted that there was a high degree of linearity
within the tested range for methane though some
nonlinearity was observed between the 6% and 20%
standard for carbon monoxide.
2.50
2.75
3.00
3.25
3.50
3.75
4.00
4.25
4.50
4.75
min
0
25000000
50000000
75000000
100000000
uV
No. SSI-GC-2103
Figure 2A: Representative Stacked Calibration Curve
Chromatograms for CP-Molesieve 5A
Figure 2B: Calibration curve for methane using the CP-
Molesieve 5A
Figure 2C: Calibration curve for carbon monoxide using the
CP-Molesieve 5A
Within the tested range of both methane and carbon
monoxide, both are observed to be nonlinear
between 1 percent and 6 percent. This may indicate a
column dependency on linear range given the
differences observed between the two molecular
sieve columns used in this analysis.
Carbonized Molecular Sieve Column Linearity
A calibration curve to test the linearity of the
Jetanizer™ with carbonized molecular sieve columns
was produced from a 0.96 ppm to approximately
20% for carbon monoxide, 0.87 ppm to
approximately 15% for methane and between 2.55
ppm and 99.99% carbon dioxide.
A linear regression analysis was performed for each
calibration curve. The following method conditions
were used:
Table 3: Method Parameters for Carbonized Molecular sieve PLOT Column
Parameter
Value
Column
GS-Carbon Plot 30 m X 0.53 mm X 3 μm (115-3133),
CarboBond 25 m X 0.53 mm X 10 μm (CP7374)
Valve Box Temperature
80° C
Injection Volume
1 mL gas sampling loop
Injector Temperature
200° C
Linear Velocity
36.6 cm/sec He
Split Ratio
7:1
Oven Ramp
Isothermal 60° C
FID Temperature
400° C
FID Gas Flows
Makeup (He): 24 mL/min, H2: 32 mL/min, Air: 250 mL/min
FID Column Insertion Depth
45 mm
Table 4: Concentrations used for calibration curve for Carbonized Molecular Sieve Columns
Concentration of Standards (ppm)
Analytes
Low TOGAS
Standard 1
Low ppm Std
Standard 2
12% CO2
Standard 3
14% CO2
Standard 4
8% CO2
Standard 5
CO2 Balance
Standard 7
Carbon Monoxide
100
0.96
59800
9900
199900
0
Methane 100
0.87
149900
60100
11900
53.5
Carbon Dioxide
400
2.55
120100
140100
78900
999935
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
min
0
10000000
20000000
30000000
40000000
50000000
uV
No. SSI-GC-2103
Figure 3A: Representative Stacked Calibration Curve
Chromatograms for GS-CarbonPLOT
Figure 3B: Calibration curve for carbon monoxide using the
GS-CarbonPLOT
Figure 3C: Calibration curve for methane using the GS-
CarbonPLOT
Figure 3D: Calibration curve for carbon dioxide using the GS-
CarbonPLOT
There was a high degree of linearity for all analytes
within the calibration curve ranges. Some nonlinearity
was observed on the 99.99% carbon dioxide standard
and 2.55 ppm carbon dioxide standard. This effect is
likely due to overloading the column in which the
method conditions could be adjusted for higher
concentrations.
1.25
1.50
1.75
2.00
2.25
2.50
min
0
50000000
100000000
150000000
200000000
250000000
300000000
350000000
uV
No. SSI-GC-2103
Figure 4A: Representative Stacked Calibration Curve
Chromatograms for CP-Carbobond
Figure 4B: Calibration curve for carbon monoxide using the
CarbonBond
Figure 4C: Calibration curve for methane using the
CarbonBond
Figure 4D: Calibration curve for carbon dioxide using the
CarbonBond
There was a high degree of linearity for all analytes
within the calibration curve ranges. Some nonlinearity
was observed on the 99.99% carbon dioxide standard
and 2.55 ppm carbon dioxide standard in a similar
behavior to the other column tested in this analysis.
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
min
0
50000000
100000000
150000000
200000000
250000000
300000000
uV
No. SSI-GC-2103
Capillary Column Analysis of Limits of Detection and
Quantitation
For limit of detection and quantitation
determinations, the following standard was selected
due to the presence of light hydrocarbons:
Table 5: Concentrations of Low TOGAS Standard (Standard 1)
Analyte
Concentration (ppm)
Methane
100
Carbon monoxide
100
Carbon dioxide
400
Acetylene
100
Ethylene
100
Ethane
100
Figure 5: Representative Chromatogram for each capillary
column with Standard 1
Table 6. Determined Limits of Quantitation from Standard 1
Results
LOQ
Concentration (ppm)
Analyte
HP-MS
CP-MS
CarboB
GS-Carb
Methane 0.6 1.4 0.7
0.7
Carbon
Monoxide
0.7
2.4
0.7
0.7
Carbon
Dioxide
N/D N/D 0.9
0.8
Acetylene
N/D
N/D
0.9
0.6
Ethylene N/D N/D 1.4
0.7
Ethane
N/D
N/D
2.5
1.3
*N/D = not determined
Table 7. Determined Limits of Detection from Standard 1
Results
LOD
Concentration (ppm)
Analyte
HP-MS
CP-MS
CarboB
GS-Carb
Methane 0.2 0.5 0.2
0.2
Carbon
Monoxide
0.2
0.8
0.2
0.2
Carbon
Dioxide
N/D N/D 0.3
0.3
Acetylene
N/D
N/D
0.3
0.2
Ethylene N/D N/D 0.4
0.2
Ethane
N/D
N/D
0.8
0.4
*N/D = not determined
No. SSI-GC-2103
Packed Column Limit of Detection and Quantitation
The packed column used for this analysis was a
custom packed carbonized molecular sieve column
which was selected to provide sufficient separation
between a composite permanent gas peak, carbon
monoxide, methane, carbon dioxide and C2
hydrocarbons while minimizing run times required.
The method conditions below were used for this
analysis:
Table 8: Parameters for Packed Carboxen Column
Parameter
Value
Column
Custom Carboxen 1006 60/80, 1 m x 1/8”
Valve Box
Temperature
80° C
Injection
Volume
1 mL gas sampling loop
Injector
Temperature
250° C
Linear Velocity
124.5 cm/sec He
Split Ratio
0.7:1
Oven Ramp
40° C hold for 2.0 min, ramp 30° C/min to
170° C hold for 6 min
FID Temperature
400° C
FID Gas Flows
Makeup (He): 24 mL/min, H2: 32 mL/min,
Air: 250 mL/min
FID Column
Insertion Depth
45 mm
Figure 6: Representative Chromatogram for Packed Carboxen
Analysis
Limits of detection were determined based on
triplicate injections of the Low TOGAS standard.
Table 9: LOD and LOQ values for Packed Column Analysis
Analyte
LOD
LOQ
Carbon monoxide
0.15
0.45
Methane
0.12
0.36
Carbon dioxide
0.11
0.33
Acetylene
0.07
0.23
Ethylene
0.12
0.35
Ethane
0.17
0.51
The overall response between the methane and
carbon dioxide was fairly consistent with the expected
concentrations. Carbon monoxide displayed a
marginally higher LOD and LOQ which is suspected to
related to inadequate separation of carbon monoxide
from the composite permanent gas peak.
■ Conclusion
The Jetanizer™ is a simple and effective way to add a
methanizer to an existing GC-2030 for both packed
and capillary columns with only a replacement of the
FID jet and no additional hardware required. The
increased ruggedness toward oxygen allows for more
simplified flowpaths compared to traditional systems.
The difference in column phase materials may play an
impact on the linearity of the detector. The more
retentive MS-5A capillary experienced more issues
with nonlinearity which may be due to adhesion of
the lower concentration analytes or other column
specific factors. Adjustments to the method such as
increasing the split ratio for higher concentrations
may aid in overcoming issues of overloading the
column and provide superior peak shape over the
displayed chromatograms. Despite column
overloading, the response was mostly linear over the
concentration ranges analyzed in this study. Further
testing at a more evenly distributed standard
concentrations may be required for a more accurate
assessment of linearity.
The limits of detection for each column and analyte
were shown to be sub-ppm levels for both the packed
and capillary columns. The lower limits of detection
and quantitation observed on the packed columns are
likely due to more standard being injected on column.
Further optimization for lower concentration analytes
could be performed but the method conditions used
were intended to meet the broad concentration range
required for linearity testing. Adverse effects from the
repeated injections of oxygen onto the Jetanizer™
were not observed during this study, indicating a
higher tolerance of oxygen than traditional
methanizers.
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First Edition: January 2021
© Shimadzu Corporation, 2021
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